Process of paving



Patented- Aug. 3, 1943 UNITED-- T OFFICE rnoosss F ravage Kenneth E. MoConna-ughay, West Lafayette, Ind.

N0 Drawing; Application February 12,

J l Serial No. 430,621

7 Claims. (01. or -23$ My invention relates to theproduction of more satisfactory and durable top surfaces on pavements. My invention is especially concerned with, but not entirely limited to, the production of better wearing surfaces on pavements of the soil-stabilization type.

In producing a pavement by soil-stabilization, the soil is first tested to determine what ingredients must be added to it to produce a pavement of the desired character, those ingredients are addedto and thoroughly mized with the soil, and the resulting mixture is thoroughly compacted. To obtain the desired degree of compaction a sheeps foot roller is ordinarily used;

and when it is necessary to produce a smooth and separates from the lower layers, thus start:

ing failures which extend into such lower layers. Attempts have been made to remedy this contention by applying a coating of bitumen, usually in the form of an emulsion, to the top layer of the pavement after compaction has been completed; but such treatment, whileit does tend to prevent failure in the top layer, does not improve the bond between the top layer and the base.

It is the primary object of my inventionto overcome the above noted disadvantages of soilstabilization pavements and to produce such a pavement having a top layer which is relatively free from a tendency to fail and which is satisfactorily bonded to the base. aspect, it is an object of my invention to improve the wearing qualities of the surface por-.

tions of pavements generally.

In carrying out my invention, I proceed as in the ordinary manner of producing a pavement by soil-stabilization through the step of compacting the stabilized soil mixture, as by the use of a sheeps foot roller. I do not, however, make any attempt to obtain an especially smooth top surface on the compacted mixture. Having mixed the soil and added ingredients, and having tamped the mixture, I then remove the surface layer to a depthof one or'two inches, mix that surface layer with bituminous binder, redistribute it over the surface of the base, and roll it to compaction. The removal of the top layer, the addition of the binder, and the redistribution and' compaction of the resulting mixture is performed fairly promptly after the original tamping of the stabilized soil and be- From a broader fore any substantial curing of the latter has occurred.

a As a result of my process, the re-mixed top layer is firmly bonded to the base, cures with the base, and is not brittle and subject to failure and dusting off under trafiic.

Preferably, the binder used in the remixing of the surface layer of the pavement is an asphaltic emulsiom A satisfactory emulsion rather generally applicable is one, hereinafter referred to as emulsion A, containing of 85 penetration asphalt, 1% saponified rosin or other emulsifying agent, and. 49% water; However, the composition and nature of the r, is capable of extensive variation. In fact, the binder need not be in the form of an emulsion, but may consist of any asphalt, cut-back, or tar which has a natural affinity for mixing with wet aggergate or which has been treated with substances, such as metal salts, rosins, animal or vegetable oils, or bentonite, capable of creating in the bituminous material a satisfactory affinity for mixing with wet aggregates.

After the surface layer of the pavement has been remixed, spread, and compacted, a seal coat may be applied if desired. A hard aggregate covering bound upon the top layer of the pavement as by such a seal coating will add to the wearing qualities of the surface.

The composition of the pavement to which my process is applied may vary considerably. Thus, the soil used may be stone, gravel, sand, cinders, clay, or combinations of such ingredients, or any type of earth. The cement em- "ployed may be Portland cement, natural cement, limestone dust, quarry waste, clay, bentonite, mixtures of bentonite with limestone dust or Portland cement, etc. In certain instances it may be desirable to incorporat an emulsion in the pavement-base. This is especially desirable when clay is used as the cement, as the emulsion will prevent a second swelling of the clay; This same result can be obtained through the use of rosin, Vinsol (a relatively hydrocarbon-insoluble natural resin), oils, and similar products.

I set forth below several examples of the applicationof my process.

Example 1.-A given soil is tested and found to require 6% to 10% of Portland cement to give proper binding and'density. The soil, over the surface to be paved, is pulverized and mixed with the dry cement, after which the requisite amount of water is added and mixing is continued. This mixing, both dry and Wet, may

' be performed by blade or other types of surface form a slab. Aiter compaction, the top one or two inches of the compacted mixture is emulsion. The composition of the emulsion used may vary widely, one which I have found satisfactory containing 55% of 150 penetration asphalt, 3% kerosene, 1% 'saponified rosin, and 86% water. This emulsion is hereinafter identified as emulsion B. The paving composition of tins example is made up follows:

' Pounds per sq.

Sand 500 Clay 108 EhiulsionB 3 After thoroughly mixing and compacting of these ingredients, I remove the top 200 pounds per square yard and mix it Withili) pounds per square yard ofemulsion A. This mixture is then dis tributed evenly over the base and compacted. An emulsion of the type identified above'as-emuh sion B might be used in remixing the top layer of the pavement, but'I- preferv to use an emulsion containing a harder bitumen, such as the emulsion identified above as emulsion A,- for the'l'iarder asphalt improves the Wearing and binding of the surface layer.

Example 3.--5i)0 pounds per square yard of gravel-say 60% of 1%; inch to V; inch particles and 40% sand-and 109 pounds of limestone dust (100 to 200-mesh) are mixed with pounds per square yard of emulsion B, and the resulting mix= ture is distributed and compacted; Following compaction, the top two inches of the slab is removed and mixed with 10 pounds'per square yard of emulsion (A or B), and the resulting mixture is spread, rolled, sealed with gallon of emulsion A per square yardand covered with 10 poundsper square yard of crushed inch to- A; inch) stone;

Example 4. 600' pounds per square yard of quarry run stone-say 60% of 1 /2 inch to 541,- inch particles and 40% of particles inch and scraped from the slab, and is mixed with 6 smaller an'd pounds per square yard of Port land cement are mixed with an appropriate quan tity or" water, and the resulting mixture" is distributed and compacted. The top 200 pounds per square yard is then scraped on, mixed with 20 pounds per square yard of emulsion (A 'or- B), redistributed over the base, and compacted. The pavement thus produced may have applied to it a sealing coat and crushed stone as in Example 3 above.

In some cases it may be found advisable before distributing the remixed surface layer over the base to prime the top surface or the base with a bituminous emulsion This is especially the case Where no bituminous" binder isincorporated in the base. i

I claimras my invention: 7

l. A process of paving by soil stabilization, comprising adding to soil ingredients necessary to of forming, distributing, and compacting said second mixture being completed before said Portland cement of the base slab has cured.

2. A process of paving by soil stabilization, comprising adding to soil ingredients necessary to produce a stable pavement, such ingredients including Portland cement, mixing the soil and added ingredients, spreading and compacting the mixture to form a slab, removing the surface portion of said slab, mixing such removed surface portiorrwith a bituminous emulsion to form a second: mixture, distributing said second mixture over the base slab, and compacting it, the steps of ioriii'ing, distributing,- and compacting said second mixture being completed before said Portland cement of the base slab has cured.

3. The process set forth in claim '1, with the addition of the step of priming the base slab with abituminous binder before distributing the second mixture over it.-

4. A process of paving by soil stabilization, comprising adding to soil ingredients necessary to produce a stable pavement, such ingredients including a binder, mixing the soil and added ingre'die'nts, spreading and compacting the mixture to form a slab, removing the surface portion of said slab, mixing such removed surface-portion with a bituminous binder to form a second mixture, distributing said second mixture over the base slab, and compacting it, the steps of forming, distributing, and compacting said second mixture being completed before said binder of th base including a bituminous binder, mixing the soil and added ingredients, spreading and compacting the mixture to form a slab, removing'the surface portion of said slab, mixing such removed surface portion with a bituminous binder to form a second mixture, distributing said second mixture over the base slab, and compacting it, the steps of forming, distributing, and compacting saidsecond mixture being completed befor said bitt'iminous binder of the base slab has cured.

6. The process set forth in claim 5 with the addition that the bitumen contained in the binder employed in the first mixture is softer than that contained in the binder employed in the second mixture,

- 7-. A process of paving, comprising the steps of spreading a mixture of aggregate and a binder, compacting such mixture to form a' slab, remov ing the surface portion of such slab, mixing such removed surface portion with a bituminous binder tororm a second mixture, distributing second mixture over said slab; and compacting it, the steps of fern n'g, distributing, and compacting said second In life being completed before said timer or thbaseslab has cured.

E. MoCQ-NNAUGHAY. 

